Selector for signal seeking tuning systems



M. J. PlFER SELECTOR FOR SIGNAL SEEKING TUNING SYSTEMS Filed April 19, 1.944.

lnventor @Homey Jan. 17, 1950 Patented Jan. 17, 1950 SELECTOR FOR SIGNA SYSTEMS 1, srcKiNe TUNING Marion J. Pifer, Williamsville, N. Y., assigner to Colonial Radio Corporation, Buffalo, N. Y.

Application April 19, i944, serial No'. v531,738 i claims. (o1. v,25o-im l This invention relates to electric automatic tuning circuits, .and more particularly to improvements in circuits of the type disclosed and yclaimed in a cci-pending application of William S. Winfield, Serial No. 463,775.

In the reference application there is disclosed an automatic tuning circuit in which the tuning instrumentality, such as a variable condenser, is driven by an electric motor. When the tuned circuit reaches resonance, which, for example, may be determined by a piezoelectric crystal associated with the circuit, the resonant voltage developed may be applied as a control voltage to a control tube to operate a series of relays which open the motor circuit and stop the tum ing variation. If it were desired to employ such a system with a large Anumber of channels, each crystal controlled for tuning accuracy, the number of crystals required and the cost of the crystals might' become excessive.

In accordance with my invention, I am able to very considerably reduce the number of crystals required by utilizing at will any one of the harmonic frequencies of a number of crystals. However, if this were all that were done, the apparatus would still be inconvenient and slow to operate because the apparatus would tune to each harmonic of the crystal in use at which a voltage developed. In accordance with my ininvention I provide means whereby the operator may select not only the particular crystal to be utilized, but also the harmonic of particular crystal, to the exclusion of others. Thus, considering `a crystal from which ythe 11thto 18th harmonics are available for tuning,.IA may, for example, select any one of these harmonics so that When the particular crystal is used, the apparatus will always tune to a selected harmonic, i. e., the 13th, 14th, 15th or whatever other harmonic frequency may have been' selected.

Also, I provide means by which the operator may select which of these harmonics he `will employ at any particular time. Thus` by using only three crystals the fundamental frequencies of which are different, and, each of which has 8 usable harmonics and selecting one at a time,

the operator has a choice` of 24 possible channels which he may utilize, it being understood, of course, that the apparatus may be so set that Aonly three channels will be available at particular previously made adjustments, it being necessary to adjust for the harmonic frequency to 'be used in case it is desired to change from' one harmonic of a crystal to afdifferent one .of the same crystal.

Accordingly, among the objects of my invention may be mentioned the following:

To provide an automatic tuning apparatus in which with appropriate preliminary adjustment, a considerably ygreater number or" channels are available for use than the number of crystals employed.

To provide a system of the class described in which a number of preselectable channels may be available from each individual crystal.

To provide apparatus in which any particular harmonic frequency of any particular crystal employed may be utilized for automatic tuning control.

Still other objects and advantages of my invention will be apparent from the specifications.

In this applicationl I have vparticularly pointed out and ,distinctly vclaimed the part, improvement, or combination which I claim as my invention or discovery, and I have explained the principles thereof and the Vbest mode in which I have ccntemplated applying those principles, so as to distinguish my invention from other inventions.

The single figure in the drawiirig` is a circuit diagram of automatic tuningapparatus in accordance with my invention. While the invern tion has `utility in either a radio receiver or transmitter, the invention is shown for purposes of illustration as ern-bodied in a transmitter arrangement of 'the ltype represented by Figure 3 of the aforementioned Winfield application. This 'transmitter includes a multiple-crystal oscillator 129i having an oscillator tube 3G indicated as one of the' triode type' having' a control grid 30g. The outputV circuit of the oscillator 29* is coupled .through a tunable `harmonic amplier 40 to a tunable output amplifier which in' turn is coupled. to an antenna A.

Referring more particularly to the tuning control system. used in: the transmitter, It represents one of several iin-icontrolled` tuners: of any suitabletype operated from shaft I I. They tuner t0 is shown as a variable condenser included :with an inductor L4 in. a tuned circuit which `may comprise one of the tunable resonant circuits of the carrier-wavev signal-'translating channel of the ampli-ner 50 or a tunable circuit coupled to the signal-translating channel. The shaft Il may in turn be driven by electric' motor I2 through. combined clutch and brake mechanism |32 and gearing i4. The oscillator 29 has' its frequency' controlled' by any one of the various crystals to be employed, such as l5, I6, and I1, by connection of the same tol the' grid 30g of the oscillator tubel 3'0 in the Well-known manner.

For purposes ofv simplicity, I have shown only 3 crystals, and circuits for controlling them, but it will be understood that as many crystals may be employed as are desired, and, as will be understood, the crystal sockets are preferably adapted to receive crystals of different frequency so that the apparatus may be readily adapted to different frequencies by the substitution of other` crystals.

The apparatus lends itself very well to pushbutton control, and in the arrangement shown I have indicated 3 pushbuttons, I8, I9, and 2U, for selection of the crystal to be employed by connecting each crystal selectively to the grid 30g of the oscillator tube 39; thus, depression ot button I8 will establish crystal I5 as the control, button I9 crystal I6, and button 2U crystal I1. In case more crystals are employed, an additional pushbutton may be used for each additional crystal. 'Ihe pushbuttons will preferably be of the well-known latch-in type, so that ,u

when one is depressed, it will remain in depressed position until another is pushed. Pushing of the second one releases the first and locks the second one in until another is pushed, and so on.

Actuation of pushbutton I8, for example, closes a circuit from ground through contacts |8a and |82) of the pushbutton, thence through the actuating winding |30 of relay lad and to a suitable source of potential, herein indicated as A+. Similarly, pushing button I9 opens the circuit of the pushbutton previously closed and closes the circuit through contacts |911 and I9?) of pushbutton I9 through the energizing winding |90 of relay ld to A+. Pushing pushbutton 2D opens the previous circuit and closes the circuit through contacts 26a, and 25h through the energizing winding 20c of relay 20d to A+.

Each of the relays preferably comprises an upper and lower set of contacts. Thus relay |8d has upper contacts ISc and lower contacts |8f. Relay |911 has upper contacts I9e and lower contacts |9f, and relay 26d has upper contacts 20e and lower contacts 2W. The lower contacts connect the ungrounded side of the respective crystals to the gride 30g of the oscillator 30. Thus relay contacts If when closed, connect the crystal I to the grid 30g of the oscillator 30, relay contacts ISf connect crystal I6 to the grid of the oscillator, and relaycontacts j connect crystal I1 to the grid of the oscillator.

It may now be understood that when pushbutton I8, for example, is depressed, the energizing winding |80 will be energized and the lower contacts If will be closed, connecting crystal I5 to the oscillator grid 39g. Also, the upper conf tacts I8e will be closed preparing a circuit which will now be described.

The control tube is indicated as at 25, having a cathode o, control grid 25g, and anode 25a. The cathode 25e may be connected to ground, the control electrode 25g connected through conductor 3| to a suitable point on a load resistor R1 of a rectifier tube 5 which with the resistor R1 is coupled across the resonant circuit I0, L4 t0 have applied thereto the resonant voltage which is developed when the circuit is in tune, and the anode 25a; on the one hand through the actuating winding 26a of relay 26, having operating contacts 265, to B+.

From the anode of tube 25 a connection may extend through resistor 21 through the upper contacts |8e of relay IBd, and to one Contact |8g on setting wheel Ih. This wheel may be conveniently supported upon shaft for rotation about the latter, but it is not driven by .shaftv and is preferably so mounted as to be frictionally retained in the angular position where it is set by manual actuation of a knob |8k which is coupled through a pinion |817 to a ring gear |87` carried by the wheel |872.. The purpose or this Inanual angular adjustment of the wheel Ih, and similarly of the Wheels I 9h and 20h, will be hereafter explained.

The contact I8g bears upon a contacting seg- Y ment |81' secured and connected to the shaft and rotatable therewith, carrying on its periphery a notch |87'. This is preferably a wiping contact of the type used in wave change switches, and cooperates with the contact Ig in a manner so that the circuit is closed between |8g and |8z' at all times except when the notch |87 is passing through the projecting fingers extending from |89.

The circuit which includes the upper contacts I9c of relay iSd may pass through similar switch elements |9g and |91' mounted on wheel |9h., which may be constructed and mounted like wheel I8h, and similarly the circuit through the upper contacts 29e of relay 20d may pass through similar contacts 20g and 20z` on Wheel 20h, similarly arranged.

Tube 25 may be the control tube of the system, and is preferably so arranged that the plate current normally flowing therethrough, when no negative bias is applied to its grid, is sufficient to hold the contacts 2Gb closed, thereby energizing the motor relay coils 21a and 21h and closing the contacts 21e in the motor circuit. 'Ihe coils 21d and 21b, which are separately shown in the drawing for purposes of clarity may be and preferably are a part of the clutch and brake mechanism indicated at I3.

The energizing circuit of the motor relay 21h may be traced from +A to the top ends of coils 21a and 21h, thence through those coils in parallel, thence through relay contacts 26h when closed, thence to ground, and when no negative bias is applied to the tube 25 by the rectier system 5,R1, the motor contacts 21e will be closed and the motor will operate, changing the tuning.

Assuming pushbutton I8 to be depressed, when a resonant voltage develops in the resonant circuit IILL4 due to the translation by the ampliner 59 of a harmonic frequency of the oscillations generated by the oscillator 29 and is applied to the rectifier 5, a negative bias is developed across the resistor R1 and is applied to the grid 25g of the control tube 25, substantially reducing the plate current in tube 25, and relay contacts 2Gb open, provided the switch on wheel I8h is open. If, however, the notch |87' is not between the fingers on IBg, this switch will be closed, and it will be seen that this switch is effectively in parallel with the control tube 25 insofar as the operation of relay 26 is concerned; that is, the plate current of tube 25 may go to zero, but relay 26 will not open if the switch on wheel lh is closed, because relay 26 is held closed by current flowing from B+ through winding 26a, resistance 21, contacts I8d and I8e, now closed, switch I 3g and I8z to ground. Similarly, the switches on wheels |9h and 20h are effectively in parallel with tube 25, but neither of these is operative unlessl its corresponding button I9 or 20 is depressed,

This will hold the motor circuit IILLl closed, and the motor will continue to operate unless the circuit tunes to a resonant frequency at a time when the switch on wheel |811, is open.

From this it will be understood that a particular crystal harmonic frequency may be set upV for encarece ipulation of the knob I'k until-the notch 487' falls between the lingers on Itg with the circuit tuned to the desired crystal harmonic. If this -is done for the various crystal harmonics, the dial may then be calibrated so that it maybe set manually by the calibration appearing upon it, to select a particular harmonic frequency, and the :same may, of course, be done for the vwheels 'IB'h and 29h, and for any additional wheels controlling additional crystals. Thereafter, the'tuning may be controlled by the pushbuttons. If 'at any time it is desired to reset the Ycircuit for' Ia vvdifferent 'harmonic of one or more-crystals, the corresponding wheel may be resetmanually'to the frequency desired, as indicated by the calibrations.

While I have shown and described certain preferred embodiments of my invention, it will be understood that modifications and 'changes may be made without departing from the spirit and scope of my invention, as will be vapparent vto those skilled in the art.

I claim:

1. In an automatic tuning system, in combination, a tuner, power driven means forvarying said tuner, a thermionic tube having a relay in its output circuit for interrupting Variation of tuning in response to the development of resonant Voltage therein, a series of push buttons each for selecting a particular frequency -channel for operation, and means associated with each push button for rendering said tube inoperative to stop the variation of tuning except over a predetermined relatively narrow'portion of the tuning range of said tuner including the channel to be selected by the respective push button, 'said last mentioned means comprising a shaft Arotatable with said tuner, and a plurality of circuit controliing members on said shaft `spaced longitudinally thereof, said circuit controlling members being angularly adjustable on said shaft to permit change of the frequency channel'to-be selected by a particular push button,

2. The combination claimed in claim -1, in which each of said circuit controlling members is a two-part rotary switch lhaving one member xedly secured to Isaid shaft, and the other surrounding said shaft, and adjustable angularly thereon.

3. In an automatic tuning system, in combination, a tuner, power driven means for varying said tuner continuously and repeatedly with a scanning action over a tuning spectrum thereof, a thermionic tube having a relay in its output circuit for controlling the energization of said power driven means to interrupt variation of tuning in response to the development of resonant voltage in a resonant circuit including said tuner, a piezoelectric crystal for establishing at least one frequency at which said resonant volttage may be developed in said resonant circuit, and an auxiliary control system including adjustable means for controlling the energization of said power driven means independently of said tube except over a small portion of the tuning spectrum ci said tuner the position of said portion within said spectrum being established by selective adjustment of said adjustable means.

4. In an automatic tuning system, in combination, a tuner, power driven means for varying said tuner continuously and repeatedly with a scanning action over a tuning spectrum thereof, a thermionic tube having a relay in its 6 output circuit for controlling the Jenergizatior'i of -said vpower driven Imeans to interrupt varia'- ition of tuning in response to the development of 4resonant voltage vin a resonant circuit including said tuner, a 'piezoelectric crystal for establishing at least one vfrequency lat which `said resonant voltage may `be 'developed in said resonant circuit, and an auxiliary control 'system includling `va manually presettable switch for control- -lingfthe energization of said power driven means independently of said tube except over a small vportion of the tuning spectrum yci said tuner,

'the 'position of said 'portion within said spectrum being 'established vby selective adjustment yof Vsaid adjustable means.

"5. In an automatic tuning system, in combination, a tuner, power driven means for Varying said tuner continuously and repeatedly `with `a scanning action over a tuning spectrum thereof, a rst control system including a thermionic tube and a relay having` la solenoid includedina space-current circuit of said tube for controlling the energization Aof said power driven means Lto interrupt variation of tuning in response "to the Ydevelopment of resonant voltage in a resonant circuit including said tuner, a' piezoelectric crystal for establishing at least one frequency at which said resonant voltage may be Adeveloped'in said resonant circuit, and an auxiliary control system including adjustable means lfor rsupplying current to said solenoid through a conductive path 'independent of said space-current circuit .of said tube for controlling the energization "of said power driven means independently of said tube except over a small Yportion vof the tuning `spectrum of said tuner, the position of said ,portion ,within said spectrum .being established "by ,selective adjustment of said adiusta'ble'means.

.6. In an automatic tuning system, 'in combination, a't'uner, power driven means for varying said tuner continuously and repeatedly with va scanning kaction over a tuning spectrum thereof, ya thermionic tube having a relay in its output .circuit for controlling the energization of said power driven means to interrupt variation o'f tuning in response to the developmentof resonant voltage in a resonant circuit including said tuner, aplurality of ,piezoelectric crystalsfor establishing the frequencies at which said resonant voltage may be developed in said resonant circuit, and an auxiliary control system including a manually presettable switch corresponding to each of said crystals for controlling the energization of said power driven means independently of said tube except over a plurality of small portions of the tuning spectrum of said tuner, the position of each of said portions within said spectrum being individually established by selective adjustment of an individual one of said switches.

7. In an automatic tuning system, in combination, a tuner, power driven means for varying said tuner continuously and repeatedly with a scanning action over a tuning spectrum thereof, a thermionic tube having a relay in its output circuit for controlling the energization of said power driven means to interrupt variation of tuning in response to the development of resonant voltage in a resonant circuit including said tuner, a plurality of piezoelectric crystals for establishing the frequencies at which said resonant voltage may be developed in said resonant circuit, means for selecting the one of said crystals to be energized during a selected operating interval, and an auxiliary control system including a man- 1-aicaxlico ually presettable switch corresponding to each of said crystals for controlling the energization of said power driven means independently of said tube except over a plurality of small portions of the tuning spectrum of said tuner, the position of each of said portions within said spectrum being individually established by selective adjustment of an individual one oi said switches.

8. In an automatic tuning system, in combination, a tuner, power driven means for varying said tuner continuously and repeatedly with a scanning action over a tuning spectrum thereof, a thermionic tube having a relay in its output circuit for controlling the energization of said lpower driven means to interrupt variation of tuning in response to the development of resonant voltage in a resonant circuit including said tuner, a piezoelectric crystal for establishing at least one frequency at which said resonant voltage may be developed in said resonant circuit, and

.an auxiliary control system including adjustable means having an element moving synchronously with said tuner for controlling the energization of said power driven means independently of said tube except over a small portion of the tuning spectrum of said tuner, the position of said portion within said spectrum being established by selective adjustment of said adjustable means.

9. In an automatic tuning system, in combination, a tuner, power driven means for varying said tuner continuously and repeatedly with a scanning action over a tuning spectrum thereof, a thermonic tube having a relay in its output circuit for controlling the energization of said power driven means to interrupt variation of tuning in response to the development of resonant voltage in a resonant circuit including said tuner, a piezoelectric crystal for establishing at least one frequency at which said resonant voltage may be developed in said resonant circuit, and an auxiliary control system including a switch structure having a first switch element moving synchronously with said tuner and a second switch element angularly presettable with relation to vsaid rst switch element for controlling energization of said power driven means independently of said tube except over a small portion of the tuning spectrum of said tuner, the position of said portion within said spectrum being established by selective adjustment of said second switch element.

10. In an automatic tuning system, in combination, a tuner, power driven means for varying said tuner continuously and repeatedly with a scanning action over a tuning spectrum thereof, a thermionic tube having a relay in its output circuit for controlling the energization of said power driven means to interrupt variation of tuning in response to the development of resonant voltage in a resonant circuit including said tuner, a plurality of piezoelectric crystals for establishing the frequencies at which said resonant voltage may be developed in said resonant circuit, and an auxiliary control system including a plurality of longitudinally spaced rotary switches each including a rst switch element moving synchronously with said tuner and a second switch element angularly presettable with relation t0 said rst switch element for controlling the energization of said power driven means independently of said tube except over small portions oi the tuning spectrum of said tuner, the position of each of said portions within said spectrum being individually established by selective adjustment of individual ones of said second switch elements.

MARION J. PIFER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Certicate of Correction Patent No. 2,495,020 January 17, 1950 MARION J. PIFER It is hereby certified that errors appear in the printed speciication of the above numbered patent requiring correction es follows:

Column 2, line 16, for the Word specifications reed spemljcatfion; iine 33, strike out one column 3, line 15, for ot before button read of; column 4, line 70, strike out 10,114 and insert the seme after circuit inline 72, same column;

and that the said Letters Patent should be read With these corrections therein that the same may conform to the record of the cese in the Patent Office.

Signed and sealed this 15th day of August, A. D. 1950.

[SEAL] THOMAS F. MURPHY,

Assistant Gommz'sszoner of Patents.

Certificate of Correction Patent No. 2,495,020 January 17, 1950 MARION J. PIFER It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction es follows:

Column 2, line 16, for the Word specifications read spemlcaton; line 33, strike out one; column 3, line 15, for ot beforefbutton read 0j; column 4, line 70, strike out 10,11* and insert the same after circuit in line 72, same column;

and that the said Letters Fatent should be read with these corrections therein that the some may conform to the record o the case in the Patent Ofee.

Signed and sealed this 15th day of August, A. D. 1950.

[SEAL] THOMAS F. MURPHY,

Assistant Commissioner of Patents. 

